Thin film magnetic heads are used extensively in data processors, such as disk drives. A typical thin film head comprises, inter alia, a nonmagnetic ceramic substrate, first and second magnetic layers that form a yoke, and an electrically conducting coil. The magnetic flux that is generated in the yoke interacts with current in the conducting coil to effectuate transducing of data signals during write and read modes. Conventionally, the first magnetic yoke layer P1 is formed as a substantially planar layer above the substrate and the second magnetic yoke layer P2 is configured in spaced relation above the P1 layer with the electrical coil interposed between the two magnetic layers. A via or through hole is provided to allow contact between the P1 layer and the P2 layer to form a back closure. An insulating layer provides the transducing gap between two pole tips at the end of the yoke structure which interfaces with a magnetic medium during reading and recording of data signals.
One problem that is experienced when operating with thin film heads is head relaxation noise, also known as popcorn noise, which is associated with the magnetic domains inherent in the yoke material. This noise manifests itself as noise spikes which adversely affect the data signal being processed. The level of noise is in proportion to the length of the domain wall that is collinearly aligned with the electrical coil turns. It is highly desirable to reduce the degrading noise and thus improve the signal-to-noise ratio.
Another factor to be considered, particularly for high frequency applications, is the efficiency of the head circuit which is related to the magnitude of circuit inductance. A lowered inductance results in an improvement in circuit efficiency.
Constant efforts have been made to reduce the noise problem and improve head operating efficiency. In an abstract delivered at the Intermag Conference in Pittsburgh in April, 1991, entitled "A Study of Popcorn Noise for Thin Film Heads", K. Morikawa et al. describe an approach for decreasing popcorn noise by narrowing the width of the yoke and/or changing the Fe composition of the magnetic Fe-Ni material used in the yoke. The abstract describes a change in the width of the yoke from 170 .mu.m to 80 .mu.m in order to reduce popcorn noise by 70%. Another article that discusses noise relaxation in thin film heads is found in an abstract by K. B. Klassen et al., IEEE Trans. Magn. MAG-25, 3212-3214 (1989). These prior art thin film heads still experience a significant level of popcorn noise and are characterized by a relatively high inductance which adversely affects the signal being processed through the heads.